This invention relates to an automatic audible signaling system and, more particularly, to such a system for use in emergency warning and direction of people in the evacuation of buildings and the like.
A number of fire-alarm systems and other automatic systems designed to activate electromechanical audible signaling devices such as bells and horns and to provide the capability of giving voice instructions by means of loudspeakers mounted in strategic locations throughout a building are known. However, conventional systems have the serious drawback that, in order to power a number of local loudspeakers mounted at remote locations, it is necessary to employ, at a central control station, an expensive, high-power amplifier. Usually, in fact, two such amplifiers are required, the second to serve as a back-up in case of failure of the main amplifier. The audio signal developed by whichever amplifier is in service must be transmitted over a considerable distance to the various speakers. Since the audio signal is a signal of high power, shock and fire hazards are presented. Moreover, the sound system must be "customized:" i.e., specially adapted to the characteristics of the fire-alarm control panel (FACP) used with it. Expensive additional control boxes and switching circuits must be devised, and, in general, a cumbersome adaptation of equipment must be made to satisfy the requirements of tone/voice capability.
A number of circuits for supervising the operation of fire-alarm systems and the like are also known. However, conventional supervisory means are comparatively complex and expensive.